Some dinosaurs stayed north: scientists

"We know they were there at the end of the dark winter period"

Here's an artist's depiction of a Hardosaur, a duck-billed dinosaur, which roamed what's now the North Slope of Alaska about 70 million years ago. (HANDOUT IMAGE)

Dinosaurs once roamed the high latitudes — and even during the dark, some stayed put, new research suggests.

Duck-billed dinosaurs in the Arctic about 70 million years ago likely endured long, dark polar winters instead of migrating to more southern latitudes, an international team of researchers has found.

The researchers published their findings, “Hadrosaurs Were Perennial Polar Residents,” in the April issue of the journal The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology, an April 11 news release said.

Anthony Fiorillo, a paleontologist at the Museum of Nature and Science, excavated 70-million-year old fossils along Alaska’s North Slope.

Most of the bones belonged to Edmontosaurus, a duck-billed vegetarian, but some others came from the fierce horned dinosaur Pachyrhinosaurus, which lived during a period marked by severe climate changes, lowered sea levels, and high volcanic activity .

The researchers found the bone microstructure of the dinosaurs provided a record of how these animals were growing throughout their lives, finding bands of fast growth and slower growth that seemed to indicate a pattern of stress.

Questioning what was causing the dinosaurs to be under stress at certain times during the year, they determined it was staying up in the polar region and dealing with reduced nutrition during the winter or migrating to and from lower latitudes during the winter.

They also could tell from the 70 million-year-old bones that the majority of the polar hadrosaurs died just after the winter season.

Most of the dinosaurs’ bones had been preserved in flood deposits.

“They are very similar to modern flood deposits that happen in Alaska in the spring when you get spring melt water coming off the Brooks Mountain Range,” said Fiorillo. “The rivers flood down the Northern Slope and animals get caught in these floods, particularly younger animals, which appear to be what happened to these dinosaurs. So we know they were there at the end of the dark winter period, because if they were migrating up from the lower latitudes, they wouldn’t have been there during these floods.”